Carrier relaying system with latched receiver



Jan. 17, 1939. M, E, RE AN 2,144,508

CARRIER RELAYING SYSTEM WITH LATCHEDRECEIVER Filed My 2, 1956 2 Sheets-Sheet 1 WITNESSES: INVENTOR 6% r I Magi/re E/feaganf ATTORNEY Jan. 17, 1939. M. E, REAGAN 2,144,508

CARRIER RELAYING SYSTEM WITH LATCHED RECEIVER Filed May 2, 1936 2 Sheets-Sheet 2 Kirk WITNESSES: INVENTOR I Ilka/ice E fiea an. y

ATTORNEY Patented Jan. 17, 1939 UNITED STATES PATENT OFFICE CARRIER RELAYING SYSTEM WITH LATCHED RECEIVER Maurice E. Reagan, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Com- REISSUED pany, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 2, 1936, Serial No. 77,531

43 Claims.

My invention relates to improvements in protective relaying systems such as are utilized for sectionalizing transmission lines in order to clear faults thereon, and it has particular relation to such a system utilizing a mechanically latched receiver-relay, for responding to a carrier current which is superimposed on the transmission system from either end of the protected linesection, or for responding to a signalling current 10 which is otherwise transmitted from either end of the protected line-section, as over separate pilot wires.

There have been several types of carrier-current protective systems utilized or proposed for 15 transmission lines prior to my present invention,

including a carrier system transmitting on alternate half-waves of the power current, a socalled intermittent carrier system, a so-called continuous carrier system, and a carrier system utilizing 20 a receiver-relay which is normally energized from a local circuit. All of these prior systems have certain drawbacks which it is my aim to overcome in my present invention. Thus, the principal drawback of the alternate-half-wave carrier 25 system is probably the one which arises from the variable phase-angle displacement in the powercurrent between the two ends of the protected line-section, although there are many other drawbacks to this particular system. The intermit- 30 tent carrier system depends, for its operation, on the initiation of the carrier-current transmission in response to an external fault, indicated at one end of the protected line-section, and the picking up of a carrier-current receiver-relay at the other end of the line-section in order to prevent faulty tripping at the second-mentioned end of the linesection, thereby involving the very serious drawback of requiring that the fault-responsive equipment at the second-mentioned end must be slowed down so as to allow for a time interval which may be of the order of 4 cycles, on a BO-cycle system, in order to allow suificient time for the receiverrelay to pick up before the local fault-responsive relay picks up, thereby slowing down the entire A5 fault-clearing operation by that much time. The

principal drawback against the continuous carrier-current relaying system is the necessity for continuously transmitting the carrier current. The carrier-current protective system utilizing 50 a receiver-relay which is normally energized from a local source of power, with means for switching control to the carrier current at times of fault, combines some advantages of the intermittent and continuous carrier systems, in that it avoids 5 most of the time-delay of the intermittent system,

and it avoids the necessity for continuously transmitting carrier, as in the continuous system, but it involves a certain time-delay incident to the collapsing of the magnetic field of the normally energized coil of the receiver-relay, and it involves a certain inflexibility, due to its multiple functions and its coil-construction, which somewhat limit its design-possibilities. A further drawback of the locally energized receiver relay is that it interposes a continuous drain on the local source of supply for energizing either the main coil or an auxiliary coil of the receiver-relay.

The principal object of my invention is to provide a mechanically latched receiver-relay which is normally latched in its actuated position and which is provided with an electrically responsive means for unlatching the same under certain fault-conditions, in combination with suitable fault-responsive relaying means, and equipment for transmitting and receiving carrier-current, constituting a protective system for a transmission line.

A more specific object of my invention is to provide an intermittent-carrier potective system utilizing a mechanically latched receiver-relay, with the sequence of operations so controlled that carrier-current is quickly superimposed on the protected line-section in response to a faultindication, and subsequently the receiver-relay is unlatched and a determination of the direction of current-flow is made, the carrier-current being removed if the current-flow is into the protected line-section.

Another object of my invention is to provide an intermittent-carrier protective system utiliz- '35 ing a receiver-relay of a type which is normally held in an actuated position by means other than the carrier-current, with controlling means for superimposing carrier-current on the protected line-section only in the event of an external 40 fault, as indicated by a fault-condition accompanied by current-flow out of the protected linesection.

A further object of my invention is to provide a protective relaying system utilizing instantaneous internal-fault and external-fault directional elements in a novel control system affecting circuit breakers and carrier-current.

Afurther object of my invention is to provide a novel form of self-resetting, mechanically latched relay suitable for use as a receiver-relay in a carrier-current protective system, and a novel protective system utilizing such a relay.

A still further object is to provide a carriercurrent protective relaying system of the meu my invention in two different illustrative preferred forms.

I have illustrated my invention as being applied toth ejprotection of a section of a threephase' transmission line I,'the 'three pha'ses being designated by the letters A, B andC. Only one end of the protected line-section is shown, since the equipment at the other end is a duplicate of the equipment at the illustrated. end. The transmission line is regarded as extending out from a bus 2 at the relaying station, and as being connected toasaid' bus "bymeans of ai'quick-acting .circuit:breaker 3. As shown in Fig. 1, the circuit breaker is provided with an auxiliaryback-contact d' which is closed when the circuit breaker is open, :anauxiliary make-contact '5 which is closed "when the circuit breaker'is closed, and a trip coil'i6 whichserves to open the circuitbreaker.

:Myrprotective system utilizes a pilot or communicating-channel between the two ends of the protected line-section,'whereby signals or intelligencemay be transmitted from'one en'dof the section to the otherffor relaying purposes. Such pilot'channel may consist of any suitable-electriccOmmunicating means,such as a highefrequency circuit for-carrier currents which are superimposed upon the protected'lin'e at oneend of the section, and which are received therefrom at both ends or at only'the far end of the protected line-section. While "I have illustrated a pilot channel utilizing these superimposed carrier currents-of high frequency, it "should be understood that such illustration is symbolic of anysuitable =pilot channel'between the two ends of the protected line-section.

As shown in the drawings, a carrier-current transmitter is indicated by a rectangle 1, and a carrier-current receiver is indicated by a rectang'le ll, the same being coupled, as'by a'transformer 9 and coupling capacitors iii, to phase C of the line I. An impedance is interposed, against the'flow of carrier-current back toward the bus 2,'by means of a choke-coil which is interposed in thephase-C conductor between the coupling capacitor 10 and the bus 2. The carrier-current transmitter l is provided with a grid-restraint circuit I3 which blocks transmission whenever'it is closed. The carrier-current receiver 8 is provided with a plate-circuit I4 which is energized whenever the receiver is prop *erly energized by a transmitted carrier current of :the frequency to which it is tuned, said receiver -being tuned, at least tothesame frequency as the transmitter at the other end of the protected line-section, and preferably it is tuned to receive from the transmitters at both ends,

wacting"fault-responsive element or elements which are illustrated, in a simple'form, as'consisting of three separateovercurrent relays 16, I7 and I8, whichareenergized from the respective phases AfBa-nd C through current-transformers l9, a1-

though other, more elaborate fault-responsive means are sometimes required, as is well known in the art; and a mechanically latched, quickacting receiver-relay 2s.

The directional element i5 is illustrated as being of the'sarne type shown in a patent of Roy M. Smith, No. 2,005,172, granted June 18, 1935. The directional element shown in Fig. 1

comprises a movable element having a normally closed back-contact 2i, and two normally open front-contacts '22 and 23, the movable element beinglconnected, at 25, to the negative bus The operating forces of the relay are applied to :two discsfid-andZd-which are operated upon by four wattmeter elements 8%, 3E, 32 and 33, of which the element 3i"! is a. so-called voltage-restraint element which normally exerts a restraining torque, as indicated by the arrow 34, tending toehold the movable element of the relay back against the back-contact, so that the backcontact 2! is closed. The voltage-restraint elementfifi 'isenergized from a suitable line-voltageresponsive potential-bus 36 which is energized from potential'networks 3T, 38 and 35*, which are shown asbeing energized from the transmission line I through capacitor potentiometers 38. The three wattmetric elements iii, 32 and 33 are clirectional elements, responsive to the three phases of the line-current and voltage, for developing an operatingtorque, as indicated by the arrows, tending to open the back-contact 2i and close the front-contacts 22 and 23 when power-current, particularly power-current of fault-magnitude and phase, is flowing away from the bus 2 and into the line-section i which is being pro- .tected.

.The overcurrent relays H, l'i' and it, which I utilize as fault-detectors in the system which I have illustrated in Fig. 1, are each provided with two sets of back-contacts ii and 42; andthree sets of fronte or make-contacts 5-3, M and 45. While these various sets: of contacts are shown, for simplicity, as being carried by a single set of fault-responsive relays, it will be readily understood that certain of the contacts may be carried by relays of different distance-settings, as is well known in the art.

The mechanically latched receiver-relay 2%) is illustrated in Fig. 1 in a form which has been .previously developed and successfully used in supervisory-control systems. It comprises an operatingcoilfil which attracts an armature 52 carried by a pivoted member which is pivoted at .53 and which terminates in an arm 54 carrying abumper 55 which presses against a spring switch-arm "56 so as to open the receiver-relay back-contacts 5'! when the receiver relay is in its actuated position. The movable armature element ofthe receiver-relay is normally biased toward its non-actuated position by means of a spring 59, but it is normally latched in its operrated position by means of a pivoted latch-member 6!! which is pivoted at 6! and which is normally biased toward its latching position by means of a springifl. The latching member 65 is actuated to unla-tch the receiver relay 2%,.by means of an unla'tching coil 63 which serves to attract an armature fi l carried by the latching lever 59.

The circuit connections between the various elements of my system are dependent upon the operation of the fault-detector means such as theovercurrent relays 16, Hand iii. The backcontacts ll of the three overcurrent relays are connected in series with each other, and in series with one of the operating coils of the voltagerestraint element of the directional element I5, so that the voltage-responsive restraint is quickly removed from the directional element I5 as soon as any one of the fault-responsive overcurrent relays I6, I1 and I8 picks up sufiiciently to open its back-contact 4I.

The back-contacts 42 of the overcurrent relays I6, I! and I8, are all connected in series with each other, and in series with the grid-restraint circuit I3 of the carrier-current transmitter I, thereby opening this grid-restraint circuit, and causing the instantaneous transmission of carrier as soon as any one of the fault-responsive overcurrent relays I6, H or I8 picks up sufilciently to open its back-contact 42.

The front-contacts 43 of the overcurrent relays I6, I I and I8 are connected in parallel to each other and in series with the unlatching coil 63 of the receiver-relay 20, so that the receiver-relay is unlatched whenever one of the overcurrent relays is actuated far enough to close its make-contact 43. It will be noted that, before this contact 43 is made, the overcurrent-relay back-contact 42 is broken, causing carrier current to be supplied to the communicating channel by the transmitter I. Thus, the operating coil 5I' of the receiver-relay is energized, and preferably its magnetizing flux is fully built up (which requires an extremely short time after the energization of the coil 5|), before the unlatching coil 63 is energized, so that the droppingout of the receiver-relay shall be under the control of the carrier current, as will now be described.

In the system shown in Fig. 1, the sequence of operation in response to a fault anywhere on the transmission line (within detecting distance of the illustrated relaying station) is first to transmit carrier, regardless of the direction of powerfiow, and then to unlatch the receiver relay, and finally to remove the carrier current, if the faultcurrent is flowing into the protected line-section I, leaving the carrier current on the line-section if the fault-current is flowing out of the section at the relaying point.

The transmission of carrier-current at one end of the protected line-section, and the maintenance of the carrier-current transmission for a period of time which is longer than the time necessary to unlatch the receiverrelay at the other end of the protected line-section, thus results in communicating, to said other end, the intelligence that there is a fault, accompanied by power-flow out of the line-section at the firstmentioned end.

As soon the a fault occurs on the transmission system, if the fault-current-fiow is into the protected line-section, the directional element I5 may, or may not, start to operate, depending upon the severity of the fault. The faultdetector relays I6, I! and/or I8 instantly respond, however, and remove voltage-restraint from the directional element, permitting the latter to operate as rapidly as possible. Before the directional element I5 can close its front con tacts 22 and 23, the overcurrent relays, or one of them, will have initiated carrier-current transmission and unlatched the receiver-relay 20, as has already been described.

After the closure of the overcurrent-relay make-contact 43, the directional-element makecontact 22 will close, provided that the fault is accompanied by power-flow into the protected line-section. As shown in Fig. 1, the directionalelement' contact 22 "re-energizes the grid-restraint circuit I3 by connecting it to the negative bus at 24,: thereby instantly blocking the generationand transmission of carrier current by the transmitter I at the relaying station. The receiver-relay coil 5| is deenergized, however, only if the carrier-current transmission is blocked at both ends of the protected line-section.

The front contacts 44 of the overcurrent relays I6, I1 and I8 are connected in parallel to each other and are utilized in the tripping of the circuit breaker 3 whenever the directional element I5 is energized (thereby closing its make-contact 23 to indicate power-flow into the line), and whenever, at the same time, the receiver-relay 20 is in its non-actuated position (thereby indicating that power is also flowing into the linesection at the other end thereof). The tripping circuit may be traced from the directional element I5, starting with the negative bus at the terminal 24 and including the front directional-relay contact 23, thence including any one of the three parallel-connected front-contacts 44 of the overcurrent relays II), N and I8, thence through the receiver-relay back-contacts 5'1, to the tripping coil 6 of the circuit breaker, the tripping circuit being finally completed through the auxiliary front-contact 5 of the circuit breaker, after which the circuit is completed at the positive bus terminal In the normal operation of the transmission system shown in Fig. 1, the circuit breaker 3 will be closed, the directional element I5 will be held against its back-contact by the voltagerestraint element 39, the three overcurrent relays I6, I! and I8 will be deenergized, and the receiver-relay 20 will be latched in its actuated position so as to open its back-contacts 51, all as illustrated in Fig. 1. The transmitter 1 will not be transmitting carrier-current because its grid-restraint circuit I3 is closed-circuited through the overcurrent back-contacts 42. The receiver 8 will not be receiving carrier-current energy because the transmitter at the opposite end of the line is likewise restrained against transmitting, by its grid circuit.

If a fault occurs on the transmission system, outside of the protected line-section I, the internal-fault-responsive directional element I5 at one end of the protected line-section I will fail to respond, because the direction of power-flow is necessarily out of the line-section at one end. As soon as an overcurrent back-contact 42 is opened, at either end of the protected line-section, the grid-restraint will be removed from the transmitter at that end of the line-section, and the transmitter i will send out carrier-current which will energize the receiver-relays 8 at both ends of the line-section, energizing the receiverrelay coils 5! so that the receiver-relays 26 will remain actuated even after they are unlatched by the energization of the unlatching coil I53 in response to the closing of an overcurrent contact 43. There will be no tripping of the circuit breaker 3 at either end of the protected linesection I, both by reason of the open frontcontacts 23 of the directional element 5 at one end of the line-section, and by reason of the open back-contacts 5! of the receiver-relay 20 at both ends of the line-section.

The transmitter 'I at one end of the line-section (where the current-flow is out of the linesection) will continue to transmit carrier-current until the fault,'wherever it is, shall be cleared by protective equipment in the line-section where the fault happens to be located, whereupon the fault-responsive overcurrent relays 16, I1 and I8 of the line-section illustrated'in the drawings'will become deenergized and return to their normal position. .It will be observed that the latching element-60 of the receiver-relay 20'must be interposed underneath the movable member 54 of the receiver-relay before the latter has moved materially from its fully actuated position in 're- .sponse to the deenergization of thereceiver-relay coil 5| from the carrier-current receiver -8, at the moment when the transmitter ceases 'transmitting. Thismay be arranged by suitable rela- 'tive adjustments of the various springs56, Hand 62, and the relative amounts of energizationof the coils 5| and 63, or other adjustments ofthe latching and unlatching times, and of the drop-out time, of the receiver-relay, and/or by a corre sponding adjustment of the relative points, in the travel of the overcurrent elements l6, l1 and I8, in which the respective front-contacts 43 open, and the back-contacts 42 close, during the dropping-out movement of the overcurrent element when it is returning to its non-actuated position; or any other suitable means may be provided to insure that the latching element 60 returns to its position under the movable member 54 of the receiver-element 20.

If the fault is in the protected line-section 'I, at least one of the overcurrent elements I6, I1 and I8 at each end of the line-section will be actuated, thereby removing voltage-restraint from its corresponding directional element '|5,'at its end of the protected line-section; and each directional element will immediately respond, opening its back-contact 2 and closingits frontcontacts 22 and 23, becausethepow'er-flow is into the line at both ends of the section. The response of the overcurrent element l6, l! or I8 will instantly initiate carrier-transmission, and immediately thereafterunlatch the receiver-relay 20, at each end of the line-section. The response of the directional elements |5 at the two ends of the line-section will removecarrler-from both ends of the section, and the receiver elements 20 will be deenergized and willinstantly return to their unactuated positions, closing their back-contacts 51 at the'two ends of the faulty line-section. A tripping circuit will be instantly energized, at each end of thesection, through the make-contact 23 of the directional'element, the make-contact 44 of one or more of the overcurrent elements l6, l1 and I8, the back-contact 51 of the receiver-relay 20, and; the auxiliary front-contact 5 of thecircuit breaker 3.

It is usual to have a contactor 61 in the tripcircuit, said contactor having make-contacts 68 which seal in, bypassing the sensitive protectiverelay contacts, and positively maintaining the tripping circuit until it is finally broken by the auxiliary breaker-switch 5.

When the circuit breaker is open, its auxiliary front-contact 5 will open the tripping circuit, and ultimately its auxiliary back-contact 4 will close, but meanwhile the overcurrent elements I6, I! and I8 will return to their unactuated positions because of the cessation of thefault-currentflow. When the auxiliary back-contact 4 of the circuit breaker closes, it energizes the actuating coil 5| of the receiver-relay 20, through a local supplycircuit from to thereby elevating the movable element 54 of the receiver-"relay, and permitting the latching member 60 to'move un derneath the same, thereby restoring the receiver-relay -20 to its normal, latched position.

,Ithas alreadybeen pointed out that, when an "external fault (that is, one outside of the protecte'd line-section) is being cleared by the operation of circuit-interrupter means outside of the protected line-section, the latching element '60 of the receiver-relay 20 must be returned to its latching position before the movable element 54 is permitted to drop from its fully actuated position, which is slightly above the top of the latching element, of course. There are various circumstances which frequently make it diflicult to obtain, this sequence of operations, because it frequently happens that one pole of the circuit breaker which is interrupting the fault-current will cease arcing before the other poles, thereby producing an asymmetrical current-flow which will have a reversed power-direction, or, in the case of a multiple-circuit transmission-line, in which there are two line-sections in parallel, the current may suddenly reverse in the sound line while the circuit breakers are in the process of opening, in the parallel faulty line, so that it is sometimes difficult to insure that carrier is not prematurely removed from the out-flowingcurrent end of a sound line-section.

Because of these difficulties, and because of the necessity for insuring that my receiver-relay latching-member shall be released by the unlatching coil 63 before the removal of carrier,

when an external fault is being cleared, I prefer to utilize some sort of power-reversal protective mechanism, such as is shown in an Evans et a1. Patent 2,005,136, granted June 18, 1935, and in a Le Vesconte et al. Patent 2,005,148, granted June 18, 1935, for interposing a predetermined time-delay (as may be determined by the exigencies of the particular transmission system under consideration) against the sudden indication of .an internal fault immediately after there has been an indication of an external fault, without interposing anydelay at all in the initial indication regarding the location of the fault.

In Fig. 1, I have indicated a novel form of power-reversal protective mechanism in whichit is not necessary to utilize a separate directional element which is responsive toexternal faults. The difilculty with using a non-action of an internalfault-responsive directional element to indicate anexternal fault is that it takes the internal element a certain time, which varies with the conditions and may be of the order of one cycle, more or less, on a Gil-cycle system, to give a reliable'directional indication, after the occurrence of a fault. In my Fig. 1 system, I therefore utilize the fault-responsive relays it, ill and it, or any one of them, to close their make-contacts 45 in response to a fault, and I use these contacts, connected in parallel, to energize an auxiliary relay H which closes its make-contacts ":2 only after a slight time-delay suiiicient to enable the directional element H) to make a reliable directional response, if it is going to respond. This slight time-delay in the auxiliary relay ll may be obtained by any suitable means, which have been symbolically designated by a dash-pot it.

tacts 15 immediately open, thereby interposing a second break in the grid-restraint circuit |3, the first break having been made at the backcontacts 42 of the fault-responsive relays l6, l1 and H3. The timer relay 14 is provided with any suitable means for delaying the reclosure of its back-contacts it after the deenergization of the relay, such time-delay means being indicated symbolically by a dash-pot 16 which delays the downward or return movement of the relay, Without delaying its piok-up movement. ternal-fault directional element 15 at first fails to respond, thereby energizing the timing relay i i, a subsequent response, opening the back-contact 2| of the directional element, will not result in an immediate blocking of the carriercurrent transmission, even though the directional-element contact 22 closes, because of the break which is interposed in the grid-restraint circuit at 75, by the timer relay M.

An important feature of the illustrated embodiments of my relaying system is that the receiver-relay 2i! must not be permitted to return to its non-actuated position, at the end of the protected line-section where current is flowing into the section, if current is flowing out of the section at the other end thereof, as the slightest touching of the receiver back-contacts will instantly trip the circuit breaker, provided, of course, that the other contacts in the trip-circuit are closed. Thus, in the system shown in Fig. 1, it is necessary for the actuating coil 5i of the receiver-relay to be sufficiently energized, by the receipt of carrier, to hold up the movable element 54 of the relay, before the unlatching ceil 53 unlatches the same. In the embodiment of my invention shown in Fig. 1, this sequence is insured by always initiating carrier-transmission in response to a fault, regardless of whether the direction of power-flow is internally or externally of the protected linesection, as this operation can be performed more quickly than a reliable directional indication may be obtained in response to the direction of power-flow.

If the power-direction is internal, at both ends of the protected line-section, the internal-fault directional elements 5 at the two ends of the line-section will remove carrier, deenergizing the receiver-relay coil 5i, and permitting the receiver-relay to drop out as soon as the magnetic flux of the operating coil 5| subsides sufficiently, assuming that meanwhile the latching element 60 has been unlatched by the energization of the unlatching coil 53, which is easily accomplished prior to the completion of the directional response. If the fault is external of the protected line-section, the power-direction will be out of the section at one end thereof, and carrier will not be removed at that end, so that, at the moment when the directional element |5 closes its make-contacts at the end where the power-flow is into the section, the receiver-relay 20 will be energized, thereby preventing tripping.

The time required to energize the tripping circuit in response to an internal fault, in the system shown in Fig. 1, is, therefore, the time required to obtain a reliable response of the directional element it plus the time required for the receiver-element to drop out, after the response of the directional element.

In the system shown in Fig. 2, I do not initiate carrier-current transmission unless there is an external fault, and the time necessary to effect the energization of the tripping circuit is, there- If the in fore, the time required to obtain a reliable external-fault directional indication, plus the time necessary to unlatch the receiver-relay, which time may be made very small by soaking a large current into the unlatching coil of the receiver-relay and by utilizing heavy biasing springs on the receiver-relay, so as to cause it to return promptly to its non-energized position.

There is thus a slightly different make-up of the times necessary to initiate the energization of the trip-circuit in the two systems shown in Figs. 1 and 2. It may sometimes happen that the system of Fig. 1 may be subject to the same difiiculty which is present in the previously known carrier-relaying system utilizing a receiver element which is normally constantly energized from a local source, even when carrier is not being transmitted, said difficulty being the time necessary for the receiver-relay flux to subside sufficiently to permit the relay to drop out, after its normally energized coil is deenergized. This time, although slight, may assume large relative proportions in a system in which it is endeavored to utilize less than one cycle, on a 60-cycle system, between the occurrence of the fault and the energization of the tripping circuit. My system shown in Fig. 2 avoids this difficulty respecting the drop-out time-lag of the receiver-relay, by not energizing the receiverrelay at all, unless the fault is external of the protected line-section.

The system of Fig. 2 utilizes the internal faultresponsive directional element 5, the fault-detector elements l6, l1 and I8 and the mechanically latched receiver-relay 20, which may be substantially the same as in the Fig. 1 system, and in addition, an external fault-responsive directional element 80 is utilized, for giving a prompt, direct indication of an external fault. In Fig. 2, the internal directional element I5 is not provided with a back-contact, but simply has a back-stop 8|, and two make-contacts 82 and 83. Each of the overcurrent elements I6, I! and I8 is provided with one back-contact 84 and three make-contacts 85, 86 and 81.

The receiver element 20 of Fig. 2 is provided, as before, with a back-contact 51, being constructed in every way similarly to the receiver relay-element 20 of Fig. 1, except that insulation 88 is inserted underneath the tip of the movable element 54 of the relay where contact is made with the top of the latching element 6|], and the latching element is connected to a source of electrical energy, such as the negative bus as indicated at 89, while the movable element 54 of the relay is connected to the terminal of the actuating coil 5|, as: indicated by the connection 90, so that, whenever the unlatching coil 63 is deenergized, thereby permitting the latching spring 62 to try to return the latching element 60 to latching position, if the receiver-relay 20 is then in its non-actuated position, a contact Will be made between the latching element 60 and the non-actuated part of the movable element 54, momentarily energizing the actuating coil 5|, and restoring the receiver relay to its normal latched position, thereby taking care of all possible contingencies in regard to the resetting of the mechanically latched receiver-relay.

The external-fault-responsive directional element 80 of the Fig. 2 system may be provided with four wattmetric torque-elements 30, 9|, 92 and 93 which are similar to the corresponding elements in Fig. 1, except that the directionally responsive torque-elements 9|, 92 and 93 are reversely connected, so as to be responsive to develop an actuating torque in response topowerflow from the line, as indicated by the arrows and legend. The external directional element 80 is provided with a back-stop 94, with a make-contact 95, and with an insulated member 96 which strikes against a contact-spring 91 and opens a back-contact 98, when the directional element moves in response to an actuating torque of the externally responsive directional members BI, 92 and 93."

In the system shown in Fig. 2, the back-contacts 84 of the overcurrent elements l6, l1 and [8. are utilized to remove voltage-restraint from both of the directional elements l5 and 80, as will be readily apparent from the drawings.

As soon as voltage-restraint is removed from the'xternal directional element 80, if the powerciurrent flowis out of the line-section, this element begins to respond, and after'the shortestpossible movement of its movable member, it strikes the spring contact-member 91 and breaks the backcontact 98, thereby removing grid-restraint from the transmitter I, by open-circuiting the gridrestraint circuit [3, causing the transmitter toimmediately initiate carrier-transmission. This energizes the actuating coil 5| of the receiverrelays 20 at both ends of the protected linesection.

Meanwhile, the internal-fault directional element I5, at the end of the line-section where the power-current flow is into the section, will respond and will close its make-contact 83. the event of an external fault, the power flow will always be into the protected section at one end and out of it at the other end, so that the internalfault directional element I5 atthe first end will begin to operate, and the external-fault direce tional element 80 at the second end will begin to: operate. similar in construction, and are energized with the same currents, their operating times should be substantially identical, particularly if the voltages supplied tcthe directional elements do not vary greatly at times of fault, as may be assured by utilizing a synchronous motor-generator. set

make contact 83, than the travel required of the tions.

0, carrier from the other end of the protected line- 99 in the voltage-supply circuit of the directional elements. The construction is such that the internally responsive element l5 must make a.

longer movement of travel, before closing its externally responsive element. 80 to break the back-contact 98, thus assuring the desired timesequence without having to introduce a. fixed.

time-delay to allow for the worst possible condi- By this time, the fault-responsive relays l6, l1 and I8 at both ends of the section will have completed their pick-up movement, closing all of their make-contacts 85, 86 and 81.

When the internally responsive directional element l5 closes its make-contact 83, therefore, a circuit is completed from the positive bus which is connected at N39 to the movable member of the directional element I 5, throughthe makecontact 83, and then through any one of the three make-contacts 85 of the overcurrent elements l6, l1 and 18, to the unlatching coil 63 of the receiver relay 20. If the receiver-relay has not been already energized by the transmission of section, as a result of a response of the externally responsive directional element 80 at that end, the

receiver-relay will immediately dropout and close its back-contacts 51, thereby closing a tripping As these two directional elements are.

' make-contact 82, any one of the three overcurrent make-contacts 86, and the receiver-relay backcontact 51-, to the trip coil 6.

In my Fig. 2 system, my power-reversal protective means takes advantage of a directional indication of an external fault, by utilizing the external directional make-contact 95 to energize a timer-relay HI I which opens its back-contact E92 and interposes a break in the grid-restraint circuit l3 of the transmitter I. The timer relay NH is energized from the external directional contact in series with any one of the overcurrent make-contacts 8.1. The timing function of the timer relay I0! is controlled by means of a dashpot I03 similar to the dashpot 16 in Fig. 1.

In the operation of the system shown. in Fig. 2, in case there is an internal fault, there will be no response of the directional element 80 at either end of the protected line-section so that carrier current will not be superimposed on the line-section at all. The closure of the internal directional contact 83 and any one of the overcurrent con.- tacts 85 will tripthe receiver-relay 28, at each end of the protected line-section, thereby instantly tripping the circuit breaker 3, as has been previously described.

As soon as the circuit breaker 3 has been tripped, the overcurrent elements it, ll and It will drop to non-energized position, and the un latching coil 63 will be deenergized, permitting the latching member 60 to close against the movable member 54 of the receiver-relay 23, thereby making a circuit, through 89 and 9B, which momentarily energizes the actuating coil 55 and relatches the receiver-relay 28, breaking the momentary latching circuit at 38, in the process.

In the event of an external fault, the faultcurrent will be flowing out of the protected linesection at one end, and the externally-responsive directional element 80 at that end will superimpose carrier current on the protected linesection and energize the receiver-relays it at both ends of the line-section before the unlatching coils 63 are energized, thereby making sure that neither one of the receiver-relays 2%, at the two ends of the section, will even momentarily drop and close its back-contact 5?. Tripping is thus positively prevented, even at the end where the power-flow is into the line-section so that the directional-relay contact 82 is closed. Also, in Fig. 2, when there is a positive indication of an external fault, an impediment is interposed against the immediate quick indication of'an internal current-flow, by means of the timer-relay contact I02. already described.

While I have referred to the invention in the foregoing description, and shall refer to it, in the accompanying claims, as involving the communication of intelligence from one end to another of a protected line-section, I wish this languageto be understood asembracing also the case of a multi-endecl section in which intelligence is communicated between more than two ends thereof, as in a T-connection.

, While Ihave illustrated my invention in two preferredforms of embodiment, it will be obvious that many changes. in details of execution may be made, without departing, from the essential principles and eifects of the, system. I desire,

consistent with their language and the prior art.

I claim as my invention:

1. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means at one end of a transmission line-section, comprising means for providing a communicating channel between the two ends of the protected line-section, electric-current means at the other end of the line-section for transmitting a signal through said communicating channel, means at said other end responsive selectively to faults accompanied by current-flow direction out of the protected line-section for transmitting a signal thereof through said communicating channel to the first-mentioned end of the protected linesection, and, at the first-mentioned end of the protected line-section, auxiliary relay-means having means for biasing it towards a non-actuated position and mechanical-latch means for latching it in actuated position, means responsive at least to faults within the protected line-section for causing said mechanically latching means to move to unlatching position, means responsive to the receipt of the aforesaid signal transmitted through the communicating channel from the other end of the protected line-section for retaining said auxiliary relay-means in its actuated position, and means for utilizing a non-actuated position of said auxiliary relay-means in the control of the circuit-interrupter means.

2. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means at one end of a transmission line-section, comprising means for providing a communicating channel between the two ends of the protected line-section, electric-current means at the other end of the line-section for transmitting a signal through said communicating channel, means at said other end responsive selectively to faults accompanied by current-flow direction out of the protected line-section for transmitting a signal thereof through said communicating channel to the first-mentioned end of the protected linesection, and, at the first-mentioned end of the protected line-section, auxiliary relay-means having means for biasing it towards a non-actuated position and mechanical-latch means for latching it in an actuated position, means responsive at least to faults within the protected line-section for causing said mechanically latching means to move to unlatching position. means responsive to the receipt of the aforesaid signal transmitted through the communicating channel from the other end of the protected line-section for actuating said auxiliary relay-means, means responsive selectively to faults accompanied by currentflow into the protected line-section, and accompanied further by a non-actuated position of said auxiliary relay-means, for quickly energizing a control circuit for the circuit-interrupter means, and means for resetting the auxiliary relay-means to its latched position.

3. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means at one end of a transmission line-section, omprising means for providing a communicating cha .nel between the two ends of the protected line-section, means at the other end of the linesection responsive selectively to faults accompanied by current-flow direction out of the protected line-section for causing a signal-current to be transmitted through said communicating channel to the first-mentioned end of the protected line-section during a time which will per- .mit the fault-responsive means at said firstmentioned end to prevent a line-sectionalizing circuit-interrupter operation, and, at the firstmentioned end of the protected line-section, receiver-relay means for receiving transmitted signal-currents in said communicating channel, said receiver-relay means being biased towards a non-actuated position, means for normally mechanically latching said receiver-relay means inan actuated position, said receiver-relay means responding to said signal-currents in such manner as to cause said receiver-relay means to move to, or remain in, its actuated position, means responsive at least to faults within the protected line-section for causing said mechanically latching means to move to unlatching position, and means responsive selectively to faults accompanied by current-flow into the protected linesection, and accompanied further by a non-actuated position of said receiver-relay means, for quickly energizing a control circuit for the circuit-interrupter means.

4. Protective relaying equipmentv for eifecting a control of line-sectionalizing circuit-interrupter means at one end of a transmission linesection, comprising means for providing a communicating channel between the two ends of the protected line-section, means at the other end of the line-section responsive selectively to faults accompanied by current-flow direction out of the protected line-section for causing a signal-current to be transmitted through said communicating channel to the first-mentioned end of the protected line-section during a time which Will permit the fault-responsive means at said first-mentioned end to prevent a line-sectionalizing circuit-interrupter operation, and, at the first-mentioned end of the protected line-section, receiver-relay means for receiving transmitted signal-currents in said communicating channel, said receiver-relay means being biased towards a non-actuated position, means for normally mechanically latching said receiver-relay means in an actuated position, said receiver-relay means responding to said signal-currents in such manner as to cause said receiver-relay means to move to, or remain in, its actuated position, means responsive selectively to faults for causing said mechanically latching means to move to unlatching position, means responsive selectively to faults accompanied by a non-actuated position of said receiver-relay means, for quickly energizing a control circuit for the circuit-interrupter means, and means for resettng the receiver-relay means to its normal latched position.

5. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel, means responsive to fault-conditions irrespective of the direction of fault-currents for quickly initiating the effective operation of said transmitter-means and for restoring the ineffective condition of the transmitter-means after the cessation of fault-conditions, receiver-relay means for receiving and responding to all signalling currents which have been transmitted into said communicating channel from either or both ends thereof, said receiver-relay means being biased towards a nonactuated position, means for normally mechanically latching said receiver-relay means in an actuated position, means responsive at least to. fault-conditions which are accompanied by current-flow direction into the protected line-section for causing said mechanically latching means to move to unlatching position at a. time.

subsequent to the energization of said receiverrelay means by a received signalling current, and for causingsaid mechanically latching means to return to latching position, in response to a cessation of fault-conditions, at a time prior to the aforesaid restoraton of the ineffective condition of the transmitter-means after the cessation of fault-conditions, means selectively responsive to fault-conditions which are accompanied by ourrent-flow direction into the protected line-section for. quickly restoring. the ineffectivev conditionv of: the transmitter-means at a time subsequent to the initiation of the effective operation of said transmitter-means, means for utilizing a nonactuated position of said receiver-relay means in the control of the circuit-interrupter means, and means for resetting the receiver-relay means to its latched position.

6. The invention as set forth in claim 5, characterized by said resetting means including an auxiliary back-contact on a circuit interrupter means for energizing the receiver-relay means.

responsive to fault conditions as distinguishedv operating conditions, a com-v from normal municating channel between the two ends of the protected line-section, meansresponsive. to a response of said fault-responsive means regardless of the direction of the fault-current for initiating the transmission of a. signal-current through said communicating channel to the far. end of the protected line-section, receiver-relay means for receiving transmitted signal-current in said communicating channel, said receiver.- relay means being biased towards a non-actuated position, means. for normally mechanically latching said receiver-relay means in an actuated position, means responsive to a. response of said. directionally responsive means for blocking. said. transmission of signal-current, means responsive to a response of said fault-responsive means for causing said mechanically latching means to move to unlatching position, means responsive to. a response of both said, directional means and, said fault-responsive means, accompanied by a non-actuated position of said receiver-relay;

means, for quickly energizing a control circuit for the circuit-interrupter meansandmeans for resetting the receiver-relay means to its normal,

latched position. 7

8. Protective relaying equipment for effecting a control ofline-sectionalizing circuit-interrupter means forv a transmission line-section, com:-.

prising, at each. end of the line-section being. pro.

tected, means for providing a communicating channel between the. two ends ofv theprotected. line-section, transmitter meanslcapableof trans. mitting a signalling. current. into said. communie. eating channel, receiver-relay means for receiv;-..

ing signalling currents which have been transmitted into saidcommunicating. channel, said" receiver-relay means; being normally biased towards a non-actuatedposition, means for normally latching; said; receiver-relay means, in. an actuated position, directionalrelay-means having directionally responsive means for developin an actuating-torquein response to current-flow into the protected: line-section and a restraining torque inresponse to-current-fiow from theprotected line section, said directional relay-means also: having a normally effective means tending to. inhibit itsoper-ation, fault-responsive means for quickly relievingsaid' normally effective inhibition and for unlatching said receiver-relay means responsiveto an actuation of said directional relay-means for quicklypreventing the transmission of a signalling current into said communicating channel at. that end of the pro tectecl; linawection, means for utilizinga nonactuated position of, said receiver-relay means in. the control of the circuit-interrupter means, and means for resetting the receiver-relay means toits latched position.

9., Rrotective relaying; equipment for efiecting a control. of. line-section'alizing circuit-interrupter means. for. a. transmission line-section, comprising, at each end-of the line-section being protected, meansfor providing acommunicating channel between: the twoends' of the protected line-section, directional relay-means having directionally responsive. means for developing an actuating torque in response to current-flowinto the protected line section and a restraining torque inresponse tocurrent-flow from the protected line-section, said directional relay-means also having a normally efiective means tending to inhibit its operation, fault-responsive means for. quickly. relieving said normally effective inhibition. and. for quickly transmitting a signalling current. into. said. communicating channel, receiver-relay means for receiving signalling currents whichhave been transmitted into said communicating. channel, said receiver-relay means being normally biased towards a nonactuated. position, means for normally latching said receiver-relay means in an actuated position, fault-responsive means for unlatching said receiver-relay means immediately after saidtransmission of a signalling current into said communicating channel, means responsive to an actuation ofsaid directional relay-means for quicklypreventing the transmission of a signalling current intorsaidcommunicating channel at that end of the protected, line-section, and means for utilizing a noneactuated position of said receiver-relay means in the control of the circuit-interrupter means. 7

10. Protective relaying equipment for effecting a control ofline-sectionalizing circuit-interrupter means-for a; transmissionline-section, comprising, at each end ofthe line-section being protected, means for providing a communicating channel between the, two ends of the protected lineesection, normally ineffective transmittermeans fortransmitting a signalling current into said communicating channel, receiver-relay means forreceiving and responding to all signalling currents which have been transmitted into said communicating channel from either or bothends thereof, said receiver-relay means'being biased towards a non-actuated condition, means other than the receiver signalling currents for.causing said receiver-relay, to be normally restrained inan actuated condition during times when there are no signalling, currents ransmitte in e er; 90....mueimties; hannel means responsive selectively to fault-conditions which are accompanied by current-flow from the protected line-section for initiating the effective operation of said transmitter-means andvfor restoring the ineffective condition of the transmitter-means after the cessation of said faultconditions, means responsive at least to faultconditions which are accompanied by currentfiow into the protected line-section for rendering ineffective the normally operative restraining means of the receiver-relay means at a time sub sequent to the time required for the initiation of the effective operation of said transmitten means, and for restoring the effective operation of said restraining means in response to a cessation of fault-conditions at a time prior to the aforesaid restoration of. the ineffective condition of the transmitter-means after the cessation of fault-conditions, and means for utilizing a nonactuated condition of said receiver-relay means in the control of said circuit-interrupter means.

11. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel, receiver-relay means for receiving and responding to all signalling currents which have been transmitted into said communicating channel from either or both ends thereof, said receiver-relay means be ing biased towards a non-actuated condition, means other than the receiver signalling currents for causing said receiver-relay to be normally restrained in an actuated condition during times when there are no signalling currents transmitted into said communicating channel, means responsive selectively to fault-conditions which are accompanied by current-flow from the protected line-section for causing the effective operation of said transmitter-means during a time which will permit the equipment at the far end of the protected line-section to prevent a line-sectionalizing circuit-interrupter operation and for restoring the ineffective condition of the transmitter-means after the cessation of said fault-conditions, means responsive selectively to fault-conditions which are accompanied by current-flow into the protected line-section for rendering ineffective the normally operative restraining means of the receiver-relay means at a time subsequent to the time required for the initiation of the effective operation of said transmitter-means, and for restoring the effective operation of said restraining means in response to a cessation of fault-conditions at a time prior to the aforesaid restoration of the ineffective condition of the transmitter-means after the cessation of fault-conditions, and means for utilizing a non-actuated condition of said receiver-relay means in the control of the circuit-interrupter means.

12. Protective relaying equipment for effect ing a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being potected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel, receiver-relay means for receiving and responding to all signalling currents which have been transmitted into said communicating channel from either or both ends thereof, said receiver-relay means being biased towards a non-actuated position, means for normally mechanically latching said receiver-relay means in an actuated position, means responsive selectively to fault-conditions which are accompanied by current-flow from the protected line-section for initiating the effective operation of said transmitter-means and for restoring the ineffective condition of the transmitter-means after the cessation of said faultconditions, means responsive at least to faultconditions which are accompanied by currentfloW into the protected line-section for causing said mechanically latching means to move to unlatching position at a time subsequent to the time required for the initiation of the effective operation of said transmitter-means, and for causing said mechanically latching means to return to latching position in response to a cessation of fault-conditions at a time prior to the aforesaid restoration of the ineffective condition of the transmitter-means after the cessation of fault-conditions, and means for utilizing a non-actuated position of said receiver-relay means in the control of said circuitinterrupter means.

13. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel, receiver-relay means for receiving and responding to all signalling currents which have been transmitted into said communicating channel from either or both ends thereof, said receiverrelay means being biased towards a non-actuated position, means for normally mechanically latching said receiver-relay means in an actuated position, means responsive selectively to fault-conditions which are accompanied by current-flow from the protected line-section for initiating the effective operation of said transmitter-means and for restoring the inefiective condition of the trans nutter-means after the cessation of said faultconditions, means responsive selectively to faultconditions which are accompanied by currentfiow into the protected line-section for causing said mechanically latching means to move to unlatching position at a time subsequent to the time required for the initiation of the effective operation of said transmitter-means, and for causing said mechanically latching means to return to latching position, in response to a cessation of fault-conditions, at a time prior to the aforesaid restoration of the ineffective condition of the transmitter-means after the cessation of fault-conditions, and means for utilizing a nonactuated position of said receiver-relay means in the control of said circuit-interrupter means.

14. The invention as set forth in claim 12, characterized by said receiver-relay means comprising an actuating coil, a movable relay-element adapted to be actuated by said actuating coil, said movable relay-element comprising biasing means tending to move the same to a nonactuated position, a movable latching element disposed in cooperative position with respect to said movable relay-element, said movable latching element comprising biasing means tending to move the same to a latched-position for holding said movable relay-element in an actuated position, an unlatching means efiective, when energized, to move said latching element to an unlatched position, and resetting means including a contact made by said latching element with said movable relay-element when the former is released and the latter is in a non-actuated'posn tion, and means responsive to said contact for momentarily actuating said actuating coil of the relay.

15. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means at one end of a transmission line-section, comprising means for providing a commum'cating channel between the two ends of the protected line-section, means at the other end of the linesection responsive selectively to faults accompanid by current-flow direction out of the protected line-section, for initiating the transmission of a signal-current through said communicating channel to the first-mentioned end of the pro tected line-section, and, at the first-mentioned end of the protected line-section, receiver-relay means for receiving transmitted signal-currents in said communicating channel, said receiverrelay means being biased towards a non-actuated position, means for normally mechanically latching said receiver-relay means in an actuated position, means responsive at least .to faults within the protected line-section for causing said mechanically latching means to move to unlatching position, and means for utilizing a non-actuated position of said receiver-relay means in the control of the circuit-interrupter means.

16. Protective relaying equipment for effecting a control of line-sectionalizing circuitinterrupter means for a transmission line-section, comprising, at each end of the line-section being protected, relaying means including a directionally responsive quick-acting relaying means selectively responsive to current-flow direction into the pro teeted line-section, and a fault-responsive quickacting relaying means selectively responsive to faul-conditions as distinguished from normal operating conditions, a communicating channel between the two ends of the protected linesection, means responsive to a response of said fault-responsive means accompanied by a. nonresponse of said directional means for causing the transmission of a. signal-current under such circumstances through said communicating chan nel to the far end of the protected line-section, receiver-relay means for receiving transmitted signal-currents in said communicating channel, said receiver-relay means being biased towards a non-actuated position, means for normally mechanically latching said receiver-relay means in an actuated position, means responsive to a response of said fault-responsive means for causing said mechanically latching means to move to unlatching position means for utilizing a nonactuated position of said receiver-relay means in the control of the circuit-interrupter means, and means for resetting the receiver-relay meansto its normal latched position.

17. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means at one end of a transmission linesection, comprising means for providing a communicating channel between the two ends of the protected line-section, means at the other end of the line-section responsive selectively to faults accompanied by current-flow direction out of the protected line-section for initiating the transmission of a signal-current through said communicating channel to the first-mentioned end of the protected line-section, and, at the first- .m-entioned end of the protected line-section, receiver-relay means for receiving transmitted signal-currents in said communicating channel, said receiver-relay means being biased towards a non-actuated position, means for normally mechanically latching said receiver-relay means in an actuated position, means responsive selec- ,tively to faults accompanied by current-flow direction into the protected line-section for causing said mechanically latching means to move to unlatching position, means for utilizing a non-actuated position of said receiver-relay means in the control of the circuit-interrupter means, and means for resetting the receiver-relay means to its normal latched position.

18 Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means at one end of a transmission linesection, comprising relaying means at the other end of the line-section including a directionally responsive quick-acting relaying means selectively responsive to current-flow direction into the protected line-section, a fault-responsive quickacting relaying means at said other end of the line-section selectively responsive to fault-conditions as distinguished from normal operating conditions, a communicating channel between the two ends of the protected line-section, means at said other end of the line-section responsive to a response of said fault-responsive means under conditions when there is a non-response of said directional means for causing the transmission of a signal-current under such circumstances through said communicating channel to the firstmentioned end of the protected line-section, and, at the first-mentioned end of the protected linesection, receiver-relay means for receiving transmitted signal-currents in said communicating channel, said receiver-relay means being biased towards a non-actuated position, means for normally mechanically latching said receiver-relay means in an actuated position, means responsive at least to fault-conditions which are accompanied by current-flow direction into the protected line-section for causing said mechanically latching means to move to unlatching position, and means for utilizing a non-actuated position of said receiver-relay means in the control of the circuit-interrupter means. 19. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel, receiver-relay means for receiving and responding to all signalling currents which have been transmitted into said communicating channel from either or both ends thereof, said receiver-relay means being biased towards a non-actuated condition, means other than the received signalling currents for causing said receiver-relay to be normally restrained in an actuated condition during times when there are no signalling currents transmitted into said communicating channel, directional relay-means having directionally responsive means for developing an internal-fault force in response to current-flow into the protected line-section and an external-fault force in response to current-flow from the protected line-section, said directional relay-means including means for indicating a response to internal-fault force and means for indicating a response to external-fault force, means responsive to an external-fault response of said directional relay-means for quickly initiating the effective operation of said transmitter-means, means responsive to an internalfault response of said directional relay-means for rendering ineffective the normally operative restraining means of the receiver-relay means after a time sufficient for said external-fault directional response to initiate the effective operation of said transmitter-means under any operative conditions of current-flow from the protected linesection, and means for utilizing a non-actuated condition of said receiver-relay means in the control of the circuit-interrupter means.

20. Protective relaying equipment for effecting a control of line-sectionalizing circuit-inter rupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel, receiver-relay means for receiving and responding to all signalling currents which have been transmitted into said communicating channel from either or both ends thereof, said receiver-relay means being biased towards a non-actuated condition, means other than the received signalling currents for causing said receiver-relay to be normally restrained in an actuated condition during times when there are no signalling currents transmitted into said communicating channel, internal-fault directional relay-means having directionally responsive means for developing an actuating force in response to current-flow into the protected line-section and a restraining force in response to current-flow from the protected line-section, said internal-fault directional relay-means also having a normally effective means tending to inhibit its operation, external-fault directional relay-means having directionally responsive means for developing an actuating force in response to current-flow from the protected linesection and a restraining force in response to current-flow into the protected line-section, said external-fault directional relay-means also having a normally eifective means tending to inhibit its operation, fault-responsive means for quickly relieving said normally effective inhibitions in both directional relay-means, means responsive to an actuation of said external-fault directional relay-means for quickly initiating the effective operation of said transmitter-means, means responsive to an actuation of said internal-fault irectional relay-means for rendering ineffective the normally operative restraining means of the receiver-relay means after a time suflicient for said external-fault directional relay-means to initiate the effective operation of said transmitter-means under any operative conditions of ourrent-flow from the protected line-section, and means for utilizing a non-actuated condition of said receiver-relay means in the control of the circuit-interrupter means.

21. Protective relaying equipment for eifecting a control of line-sectionali ing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel, receiver-relay means for receiving and responding to all signalling currents which have been transmitted into said communicating channel from either or both ends thereof, said receiver-relay means being biased towards a non-actuated condition, means other than the received signalling currents for causing said receiver-relay to be normally restrained in an actuated condition during times when there are no signalling currents transmitted into said communicating channel, directional relay-means having directionally responsive means for developing an internal-fault force in response to current-flow into the protected line-section and an external-fault force in response to current flow from the protected line-section, said directional relay-means including means for indicating a response to internal-fault force and means for indicating a response to external-fault force, means responsive to an external-fault response of said directional relay-means for quickly initiating the efie'ctive operation of said transmittermeans, means responsive at least to faults within the protected line-section for rendering ineffective the normally operative restraining means of the receiver-relay means after a time suflicient for said external-fault directional response to initiate the effective operation of said trans-= mitter-means under any operative conditions of current-flow from the protected line-section, and

means for utilizing a non-actuated condition of said receiver-relay means in the control of the circuit-interrupter means 22. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interruptor means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel receiver-relay means for receiving and responding to all signalling currents which have been transmitted into said communicating channel from either or both ends thereof, said receiver-relay means being biased towards a non-actuated condition, means other than the received signalling currents for causing said receiver-relay to be normally restrained in an actuated condition during times when there are no signalling currents transmitted into said communicating channel, internal-fault directional-relay-means having directionally responsive means for developing an actuating force in response to current-flow into the protected linesection and a restraining force in response to current-flow from the protected line-section, said internal-fault directional relay-means also having a normally efiective means tending to inhibit its operation, externalault directional relay-means having directionally responsive means for developing an actuating force in response to current-flow from the protected line-section and a restraining force in response to current-flow into the protected line-section, said externalfault directional relay-means also having a normally effective means tending to inhibit its operation, fault-responsive means for quickly relieving said normally effective inhibitions in both directional relay-means, means responsive to an actuation of said external-fault directional relay-means for quickly initiating the efiective operation of said transmitter-means, means refault directional relay-means to initiate the effective operation of said transmitter-means under any operative conditions of current-flow from the protected line-section, and means for utilizing a non-actuated condition of said receiver-relay means in the control of the circuit-interrupter means.

23. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel, receiver-relay means for receiving signalling currents which have been transmitted into said communicating channel, said receiver-relay means being normally biased towards a non-actuated position, means for normally latching said receiver-relay means in an actuated position, internal-fault directional relay-means having directionally responsive means for developing an actuating force in response to current-flow into the protected line-section and a restraining force in response to current-flow from the protected line-section, said internal-fault directional relay-means also having a normally effective means tending to inhibit its operation, external-fault directional relay-means having directionally responsive means for developing an actuating force in response to current-flow from the protected line-section and a restraining force in response to current-flow into the protected line-section, said external-fault directional relay-means also having a normally effective means tending to inhibit its operation, fault-responsive means for quickly relieving said normally effective inhibitions in both directional relay-means, means responsive to an actuation of said external-fault directional relaymeans for quickly initiating the effective operation of said transmitter-means, means responsive to an actuation of said internal-fault directional relaymeans for unlatching the receiver-relay means after a time sufficient for said external-fault directional relay-means to initiate the eifective operation of said transmitter-means under any operative conditions of current-flow from the protected line-section, and means for utilizing a non-actuated position of said receiver-relay means in the control of the circuit-interrupter means.

24. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel, receiver-relay means for receiving signalling currents which have been transmitted into said communicating channel, said receiver-relay means being normally biased towards a non-actuated position, means for normally latching said receiver-relay means in an actuated position, internal-fault directional relaymeans having directionally responsive means for developing an actuating force in response to ourrent-flow into the protected line-section and a responsive to an actuation of said external-fault directional relay-means for quickly initiating the effective operation of said transmitter-means, means responsive at least to faults within the protected line-section for unlatohing the receiverrelay means after a time suflicient for said external-fault directional relay-means to initiate the effective operation of said transmitter-means under any operative conditions of current-flow from the protected line-section, and means for utilizing a non-actuated position of said receiver- I relay means in the control of the circuit-interrupter means.

25. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means at one end of a transmission line-section, comprising means for providing a communicating channel between the two ends of the protected line-section, means at the other end of the linesection responsive selectively to faults accompanied by current-flow direction out of the protected line-section for causing a signal-current to be' transmitted through said communicating channel to the first-mentioned end of the protected line-section during a time which will permit the fault-responsive means at said first mentioned end to prevent a line-sectionalizing circuit-interrupter operation, and for maintaining said transmission of signal-current for a predetermined time after any sudden reversal of currentiiow direction during a continuance of said faults, and-at the first-mentioned end of the protected line-section, receiver-relay means for receiving transmitted signal-currents in said communicating channel, said receiver-relay means being biased towards a non-actuated position, means for normally mechanically latching said receiverrelay means in an actuated position, said receiverrelay means responding to said signal-currents in such manner as to cause said receiver-relay means to move to, or remain in, its actuated position, F

means responsive at least to faults within the protected line-section for causing said mechanically latching means to move to unlatching position, and means for utilizing a non-actuated position of said receiver-relay means in the control of the circuit-interrupter means.

26. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected inc-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel, means responsive to fault-conditions irrespective of the direction of fault-currents for quickly initiating the effective operation of said transmitter-means and for restoring the ineffective condition of the transmitter-means after the cessation of fault-conditions, receiver-relay means for receiving and responding to all signalling currents which have been transmitted into said communicating channel from either or both ends thereof, said receiverrelay means being biased towards a non-actuated position, means for normally mechanically latching said receiver-relay means in an actuated position, means responsive at least to fault-conditions which are accompanied by current-flow direction into the protected line-section for causing said mechanically latching means to move to unlatching position at a time subsequent to the energization of said receiver-relay means by a received signalling current, and for releasing said mechanically latching means, in response to a cessation of fault-conditions, at a time prior to the aforesaid restoration of the ineffective condition of the transmitter-means after the cessation of faultconditions, means selectively responsive to faultconditions which are accompanied by currentflow direction into the protected line-section for quickly restoring the ineffective condition of the transmitter-means at a time subsequent to the initiation of the effective operation of said transmitter-means, means directionally responsive to a fault-condition accompanied by current-flow from the protected line-section for thereafter inter posing an impediment to any immediate qm'ck prevention of signal-current transmission into the communicating channel at that end of the protected line-section, means for utilizing a nonactuating position of said receiver-relay means in the control of the circuit-interrupter means, and means for resetting the receiver-relay means to its latched position.

27. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, transmitter-means capable of transmitting a signalling current into said communicating channel, receiver-re1ay means for receiving slgnailing currents which have been transmitted into said communicating channel, said receiver-relay means being normally biased towards a non-actuated position, means for normally latching said 'receiver-relay means in an actuated position,

fault-responsive directional relay-means having directionally responsive means for developing an actuating force in response to current-flow into the protected line-section and a restraining force in response to current-flow from the protected line-section, fault-responsive means for unlatching said receiver-relay means, means responsive to an actuation of said directional relay-means for quickly preventing the transmission of a signalling current into said communicating channel at that end of the protected line-section, means directionally responsive to a fault-condition accompanied by current-flow from the protected line-section for thereafter interposing an impediment to any immediate quick prevention of signalcurrent transmission into the communicating channel at that end of the protected line-section, means responsive to a non-actuated position of said receiver-relay means for energizing a control circuit for the circuit-interrupter means, and means for resetting the receiver-relay means to its latched position.

28. Protective relaying equipment for effecting a control. oi line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, fault-responsive directional relaymeans having directionally responsive means for developing an actuating force in response to ourrent-flow into the protected line-section and a restraining force in response to current-flow from the protected line-section, fault-responsive means for quickly transmitting a signalling current into said communicating channel, receiver-relay means for receiving signalling currents which have been transmitted into said communicating channel, said receiver-relay means being normally biased towards a non-actuated position, means for normally latching said receiver-relay means in an actuated position, fault-responsive means for unlatching said receiver-relay means immediately after said transmission of a signalling current into said communicating channel, means responsive to an actuation of said directional relay-means for quickly preventing the transmission of a signalling current into said communicating channel at that end of the proteoted line-section, means directionally responsive to a fault-condition accompanied by currentflow from the protected line-section for thereafter interposing an impediment to any immediate quick prevention of signal-current transmission into the communicating channel at that end of the protected line-section, means responsive to a non-actuated position of said receiverrelay means for energizing a control circuit for the circuit-interrupter means, and means for resetting the receiver-relay means to its latched position.

29. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel, receiver-relay means for receiving and responding to all signalling currents which have been transmitted into said communicating channel from either or both ends thereof, said receiver-relay means being biased towards a non-actuated position, means for normally mechanically latching said receiverrelay means in an actuated position, means, responsive selectively to fault-conditions which are accompanied by current-flow from the protected line-section, for initiating the effective operation of said transmitter-means, and for restoring the inefiective condition of the transmitter-means after the cessation of fault-conditions, and for maintaining said transmission of signal-current for a predetermined time after any sudden reversal of current-flow direction during a continuance of said fault-conditions, means responsive at least to fault-conditions which are accom panied by current-flow into the protected linesection for causing said mechanically latching means to move to unlatching position at a time subsequent to the time required for the initiation of the effective operation of said transmittermeans, and for causing said mechanically latching means to return to latching position, in response to a cessation of fault-conditions, at a time prior to the aforesaid restoration of the ineffective condition of the transmitter-means after the cessation of fault-conditions, and means for utilizing a non-actuated position of said receiver-relay means in the control of said circuitinterrupter means.

30. Protective relaying equipment for effecting a control. of line-se-ctionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being pro tected, means for providing a communicating channel between the two ends of the protected line-section, transmitter-means capable of transmitting a signalling current into said communicating channel, receiver-relay means for receiving signalling currents which have been transmitted into said communicating channel, said receiverrelay means being normally biased towards a non-actuated condition, directional relay-means having directionally responsive means for developing an actuating force in response to current-flow into the protected line-section and a restraining. force in response to current-flow from the protected line-section, said directional relay-- means being normally biased towards a nonactuated condition, means responsive to a faultcondition accompanied by an actuated condition of said directional relay-means for quickly preventing the transmission of a signalling current into said communicating. channel at that end of the protected line-section, means responsive, after a time-delay, to a fault-condition accompanied by a non-actuated condition of said directional relay-means, for thereafter interposing an impediment to any immediate quick prevention of signal-current transmission into the communicating channel at that end of the protected linesection, and means for utilizing said receiverrelay means in the control of said circuit-interrupter means.

31. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between. the two ends of the protected line-section, directional relay-means having directionally responsive means for developing an t actuating force in response to current-flow into the protected line-section and a restraining force in response to current-flow from the protected line-section, said directional relay-means being normally biased towards a non-actuated condition, fault-responsive means for quickly transmitting a signalling current into said communicating channel, receiver-relay means for receiving signalling currents which have been transmitted into said communicating channel, said receiverrelay means being normally biased towards a non-actuated condition, means responsive to a fault-condition accompanied by an actuated condition of said directional relay-means for quickly preventing the transmission of a signalling current into said communicating channel at that end of the protected line-section, means responsive, after a time delay, to a fault-condition, accompanied by a non-actuated condition of said directional relay-means for thereafter interposing an impediment to any immediate quick pre= vention of signal-current transmission into the communicating channel at that end of the prctected line section, and means for utilizing said receiver-relay means in the control of said circuit-interrupter means.

32. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmissionline-section, comprising internal-fault directional relay-means having directionally responsive means for developing an actuating force in response to. current-flow into tive inhibition, means for obtaining an externalfault directional response to faults accompanied by current-flow from the protected line-section, said last-mentioned means comprising means responsive after a time delay, to a fault-condition, accompanied by a non-actuated condition of said internal-fault directional,relay-means, and means for utilizing said various responses in the control of said circuit-interrupter means.

33. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmittermeans for transmitting a signalling current into said communicating channel, receiver-relay means for receiving and responding to all signalling currents which have been transmitted into said communicating channel from either or both ends thereof, said receiver-relay means being biased towards a non-actuated condition, means independent of the received signalling currents for causing said receiver-relay means to be normally restrained in an actuated condition during times when there are no signalling currents transmitted into said communicating channel, means, responsive selectively to fault-conditions which are accompanied by current-flow from the protected line-section, for causing the efiective operation of said transmitter-means during a time when relaying operations are in process, and

for restoring the inefiective condition of the transmitter-means after the cessation of faultconditions, and for maintaining said transmission of signal-current for a predetermined time after any sudden reversal, of current-flow direction during a continuance of said fault-conditions, means responsive at least to faults within the protected line-section for rendering inefiective the normally operative restraining means of the receiver-relay means, and means for utilizing .a non-actuated condition of said receiver-relay means in the control of the circuit-interrupter means.

34. Protective relaying equipment foreffecting a control. of line-'sectionalizing circuit-interrupter means at one end of a transmission-line section, comprising normally inefiective transmitter means at the other end of the line-section for transmitting a signal-current from its end to the first-mentioned end of the line-section, means at said. other end responsive to faults accompanied by current-flow direction out of the protectedline-section at that end for causing the effective operation of said transmitter means during a time when the circuit-interrupter operation should be blocked, normally inactive circuit-interrupter operating means at the first-mentioned effectively operative, to cause said receiver'relay to move to its tripping position, said trip-position means including a normally-deenergized electriccirouit and relay-coil combination and means for energizing the same only in accordance with a predetermined manner of response to an actual fault-condition on the transmission line, and electro-responsive means including a normally deenergized electric-circuit and relay-coil combination which is energized only in response to an effective received signal-current for blocking the movement of the receiver relay to its tripping position.

35. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means at one end of a transmission-line section, comprising normally ineffective transmitter means at the other end of the line-section for transmitting a signal-current from its end to the first-mentioned end of the line-section, means at said other end responsive to faults accompanied by current-flow direction out of the protected line-section at that end for causing the efiective operation of said transmitter means during a time when the circuit-interrupter operation should be blocked, normally inactive circuit-interrupter operating means at the first-mentioned end including a receiver relay having a tripping condition and .a normal non-tripping condition, normally ineffective trip-condition means tending, when efiectively operative, to cause said receiver relay to change to its tripping condition, means responsive to an effective received signalcurrent for restraining the change of said receiver relay to its tripping condition, and additional means independent of the signal-current for selectively responding to faults accompanied by current-flow direction into the protected linesection and for rendering said trip-condition means effective in the absence of said blocking action. a

36. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means at one end of a transmission-line section, comprising normally ineffective transmitter means at the other end of the line-section for transmitting a signal-current from its end to the first-mentioned end of the line-section, means at said other end responsive to faults accompanied by current-flow direction out of the protected line-section at that end for causing the eifective operation of said transmitter means during a time when the circuit-interrupter operation should be blocked, normally inactive circuit-interrupter operating means at the first-mentioned end including an electro-magnetic receiver relay having a tripping position and a non-tripping position, holding means effective during normal times when there is no efiective signal-current and when there is no fault on the transmission line for normally holding the receiver relay in its non-tripping position, trip-position means in addition to said holding means and tending, when effectively operative, to cause said receiver relay to move to its tripping position, said trip-position means including a normally deenergized electriccircuit and relay-coil combination and means for energizing the same only in accordance with a predetermined manner of response to currentflow direction into the line-section, and electroresponsive means including a normally deenerized electric-circuit and relay-coil combination which is energized only in response to an effective received signal-current for blocking the movement or the receiver relay to its tripping position.

3'7. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means at one end of a transmission-line section, comprising normally ineffective transmitter means at the other end of the line-section for transmitting a signal-current from its end to the first-mentioned end of the line-section, means at said other end responsive to faults accompanied by current-flow direction out of the protected line-section at that end for causing the eifective operation of said transmitter means during a time when the circuit-interrupter operation should be blocked, normally inactive circuit-interrupter operating means at the firstinentioned end including an electro-magnetic receiver relay having a tripping position and a non-tripping position, holding means effective during normal times when there is no effective signal-current and when there is no fault on the transmission line for normally holding the receiver relay in its non-tripping position, trip posi tion means in addition to said holding means and tending, when efifectively operative, to cause said receiver relay to move to its tripping position,

said trip-position means including a normally deenergized electric-circuit and relay-coil combination and means for energizing the same only in accordance with a predetermined manner of response to an actual fault-condition on the transmission line accompanied by current-flow direction into the protected line-section, and electro-responsive means including a normally deenergized electric-circuit and relay-coil combination which is energized only in response to an effective received signal-current for blocking the movement of the receiver relay to its tripping position.

38. Protective relaying equipment for efiecting a control of line-sectionalizing circuit-interrupter means for a transmission-line section, comprising, at each end of the line-section being protected, normally inactive transmitter means for transmitting a signal-current from its end to the other end of the line-section, normally inactive circuit-interrupter operating means including an electro-magnetic receiver relay having a tripping position and a non-tripping position, holding means effective during normal times when there is no effective signal-current and when there is no fault on the transmission line for normally holding the receiver relay in its non-tripping position, trip-position means in addition to said holding means and tending, when effectively operative, to cause said receiver relay to move to its tripping position, said trip-position means including a normally deenergized electric-circuit and relay-coil combination, and electro-responsive means including a normally deenergized electrio-circuit and relay-coil combination which is energized only in response to an effective received signal-current for blocking the movement of the receiver relay to its tripping position, fault-responsive means operative, in the absence of other inhibitions, to remove an impediment against the effective operation of said transmitter means and to energize said normally deenergized electric-circuit and relay-coil combination of said trip-position means, said fault-responsive means being responsive by an operative change in its condition as a result of faults on the transmission line, and directionally responsive means operative, in the absence of other inhibitions, to interpose an impediment against the effective operation of the transmitter means, said directionally responsive means being responsive by an opera- 9: mitting a slgnalllng current into sa1d communia normal non-tripping condition, directional remeans at the other end of the line-section for tive change in its condition as a result of current-flow direction into the protected line-secacontrol of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, ateach end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, transmitter-means capable of transcating channel, receiver-relay means for receiving signalling currents which have been transmitted through said communicating channel, said receiver-means having a tripping condition and lay-means having directionally responsive means for developing an actuating force in response to current-flow into the protected line-section and a restraining force in response to current-flow from the protected line-section, said directional relay-means being normally biased towards a non-actuated condition, means responsive to a fault-condition accompanied by an actuated condition of said directional relay-means for blocking the transmission of a signalling current into said communicating channel at that end of the protected line-section, means responsive, after a time delay, to a fault-condition accompanied by a non-actuated condition of said directional relay-means, for thereafter interposing an impediment against any immediate blocking of signalcurrent transmission into the communicating channel at that end of the protected line-section, and means for utilizing said receiver-relay means in the control of said circuit-interrupter means.

40. Protective relaying equipment for effecting comprising normally ineffective transmitter transmitting a signal-current from its end to the first-mentioned end of the line-section, faultresponsiveimeans at said other end for quickly initiating the transmission of said signal-current at said other end, internal directional means at said other end'for blocking the transmission of said signal-current at said other end when there is a predetermined current-flow in a direction into the protected line-section at said other end, meansv responsive, after a time-delay, to a faultcondition accompanied by a non-actuated condition of said internal directional means at said other .end, for thereafter interposing an impediment against any immediate blocking of signalcurrent transmission into the communicating channel at said other end of the line section, and normally inactive circuitrinterrupter operating means at the first-mentioned end .of the linesection including a receiver relay having a tripping condition and a normal non-tripping condition, normally ineffective trip-condition rneans tending, when effectively operative, to cause said receiver relay to change to its tripping condition, means responsive to an effective received signalcurrent for blocking the change of said receiver relay to its tripping condition, and means responsive in a predetermined manner to faults on the transmission line for rendering said tripcondition means effective in the'absence of said blocking action.

means atone end of a transmission-line section,

comprising normally ineffective transmitter means at the other end of the line-section for transmitting a signal-current from its end to the first-mentioned end of the line-section, fault-r responsive means at said other end for quickly initiating the transmission of said signal-current at said other end, internal directional means at said other end for blocking the transmission of said signal-current at said other end when there is a predetermined current-flow in a direction into the protected line-section at said other end, means responsive, after a time-delay, to a fault,- condition accompanied by a non-actuated condition of said internal directional means at said other end, for thereafter interposing an impediment against any immediate blocking of signal-i current transmission into the communicating channel at said other end of the line-section, and normally inactive circuit-interrupter operating means at the first-mentioned end of the line-section including an electro-magnetic receiver relay having a tripping position and a non-tripping position, holding means effective during normal times when there is no effective signal-current and when there is no fault on the transmission line for normally holding the receiver relay in its non-tripping position, tripposition means in addition to said holding means and tending, when effectively operative, to cause said receiver relay to move to its tripping position, said trip-position means including a normally'deenergized electric-circuit and relay-coil combination and means for energizing the same only in accordance with a predetermined manner of response to an actual fault-condition on the transmission line, and electro-responsive means including a normally ,deenergized electric-circuit and relay-coil combination which is energized only in response to an effective received signalcurrent for blocking the movement of the receiver relay to its tripping position.

42. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends ofthe protected line-section, directional relay-means having directionally responsive means for developing an actuating force in response to current-flow into the protected line-section and a restraining force in response to current-flow from the protected line-section, said directional relay-means being normally biased towards a non-actuated condition, fault-responsive means for quickly transmitting a signalling current into said communieating channel, means responsive to a faultcondition accompanied by an actuated condition of said directional relay-means for blocking the transmission of signalling current at its end of the protected line-section, receiver-relay means having a tripping condition and a non-tripping condition, restraining means effective during normal times when there is no effective signalecurrent and when there is no fault on the transmission line for normally restraining the receiver relay in its non-tripping condition, trip-condition means in addition to said restraining means. and tending, when effectively operative, to cause said receiver relay to change to its tripping condition, means responsive to an effective signal-current received from the other end of the protected linesection for restraining the change of said receiver relay to its tripping condition, and means responsive in a predetermined manner to faults on the transmission line for rendering said tripcondition means efiective in the absence of said blocking action.

43. Protective relaying equipment for efiecting a control of line-sectionalizing circuit-interrupter mans for a transmission line-section, comprising, at each end of the line-section being protected, means for providing a communicating channel between the two ends of the protected line-section, normally ineffective transmitter-means for transmitting a signalling current into said communicating channel, receiver-relay means for receiving and responding to all signalling currents which have been transmitted into said communicating channel from either or both ends thereof, means other than the received signalling currents for causing said receiver-relay means to be normally restrained in a non-tripping condition during times when there are no signalling current transmitted into said communicating channel, means responsive to an effective received signalling current for restraining said receiver-relay means in a non-tripping condition, means, responsive selectively to fault-conditions which are accompanied by current-flow from the protected line-section, for causing the efiective operation of said transmitter-means during a time when relaying operations are in process, and for maintaining said transmission of signal-current for a predetermined time after any sudden reversal of current-flow direction during a continuance of said fault-conditions, means responsive at least to faults Within the protected line-section for causing the receiverrelay means to assume a tripping condition in the absence of an efiective received signalling current, and means for utilizing the tripping condition of said receiver-relay means in the control of the circuit-interrupter means.

MAURICE E. REAGAN. 

